The present invention relates to the field of capacitive detection devices and their applications to measuring devices, in particular measuring displacements, fluid levels, thicknesses notably of fluid film and presence detection.
It is known practice to produce capacitive detectors which comprise, on one face of a ribbon made of a dielectric material, two electrodes in the form of combs whose branches are arranged alternately between one another, or interdigitally, and, on the other face, a ground electrode. It is known that the presence of the ground electrode makes it possible by a three-wire measurement to increase the sensitivity of the device, and to protect it from stray external effects. In general, it is considered that the capacitance between the interdigital electrodes of such a device is the sum of a dielectric contribution inside the ribbon and of another dielectric contribution on the outer part of the plane of the electrodes, which comes from vacuum or from a fluid.
Moreover, the international patent application published under the number WO2009/122061 describes a capacitive detector whose features make it possible to increase the sensitivity of such capacitive detectors.
The European patent application published under the number 0 508 143 describes a capacitive measurement device which comprises an outer electrode situated on the outside of a container and an inner electrode situated inside this container. These electrodes constitute a measurement capacitance in relation to fluids circulating in the container. The useful measured variable consists of the electrical signal deriving from this capacitance.